Except that I didn’t advise doing that, I said that voip-info did and speculated that possibly the phone’s directives WERE limiting the incoming rtp range but that I’d test that. And after testing, it’s clear they don’t.
However I don’t have a huge amount of sympathy for the OP being confused by hijacking this to dive into RTP - he didn’t provide a writeup of his environment and in some cases I had to ask multiple times for information before getting it. He started out with 2 problems - phone registration - and phone connectivity to the softphones he’s using - and clearly jumped to conclusions that “linphone is doing it right and the Cisco 7941G was broken in some manner” once he got the 7941G registered.
When in reality, I’ve NOT been able to duplicate his problem with other phones and other softphones communicating to the 7961G (which uses the same code) EXCEPT when using linphone.
And further Googling shows a LOT of people complaining about linphone being broken in other environments in the past.
Linphone’s code is OSS:
So my recommendation is either diagnose the problem and submit a patch, or at least submit a bug (although they likely will want SIP traces) or use something other than linphone.